Disinfecting a container, in particular in the food industry, is generally carried out using fluids and, if necessary, by additional mechanical treatment. In addition, sulfur dioxide (SO2) gas is traditionally used for disinfecting wooden barrels. For this purpose, for example sulfur sticks are burned or carbonized inside the wooden barrel.
In addition to the biocidal effect of sulfur dioxide gas, the biocidal effect of sulfites takes place in aqueous solution that, for example can be obtained through solution equilibriums between the gas phase and (residual) moisture on surfaces, primarily through the undissociated form of sulfuric acid (H2SO3). In order for the latter to achieve an optimum effect, a low pH value is thus required, preferably below 3. Consequently, this means that the containers used for foodstuff, in particular wooden barrels, have to be freed from degradation products and acidic residues by cleaning with sterile water after the sterilization process. For complete removal and disinfection, this has to be done thoroughly and therefore involves significant expenditure of time.
The biocidal effect of sulfur dioxide and the sulfites is in particular based on their reduction effect. In the process of this, the available oxygen is rapidly absorbed by sulfur dioxide and the sulfites so that the aerobic organisms cannot perform a metabolic process and consequently die off. In contrast, the biocidal effect with respect to anaerobic microorganisms is poor.
Furthermore, using sulfur dioxide for disinfecting wooden barrels results in the wood absorbing the disinfecting sulfur dioxide gas, and residues of sulfur dioxide are still present in the wood, even after extensive cleaning with water. After filling the barrels with foodstuff such as, for example wine, these residues are released into the food stuff, which can result in excessive sulfite contents. In view of the biocidal effect of the sulfites, this poses an undesirable health burden. Uncombined sulfites are known for causing pseudoallergic and anaphylactic reactions after inhalation and oral ingestion. Furthermore, sulfites are a skin and mucosa irritant.